The invention relates to switching core controllers for controlling switching cores, and modes of operation therefor.
Digital Cross-connect Systems (hereinafter referred to as xe2x80x9cDCSsxe2x80x9d), for example, the T::DAX(trademark) DCS commercially available from the proprietor of the present application, are regarded as so-called static switching devices due to their relatively slow switching capability in comparison to switches. DCSs are typically employed for slow switching purposes, for example, bandwidth management purposes, grooming, conversion between transmission standards, and the like.
In a Bellcore white paper entitled xe2x80x9cArchitecture Solutions to Internet Congestion Based on SS7 and Intelligent Network Capabilitiesxe2x80x9d by Dr. Amir Atai and Dr. James Gordon, there are proposed several pre-ingress switch and post-ingress switch internet call offload architectures for reducing internet call traffic congestion in the Public Switched Telephone Network (PSTN). One particular post-ingress switch implementation is based on the deployment of a Class 4 Tandem Replacement Switch with Signaling System No. 7 (SS7) capabilities, for example, the ICS2000 Integrated Convergence Switch commercially available from Convergent Networks, GSX9000 Open Services Switch commercially available from Sonus, amongst others (see FIG. 1). Such Tandem Replacement Switches are typified by a switching core having a high switching rate capability.
Dial up internet connection often requires several attempts before a successful connection is made, particularly during the internet call busy period between about 9 pm to midnight. To obtain an internet connection in the case of a busy tone, a subscriber may re-dial the same access number or try another dial up internet access telephone number of his ISP which is awkward and time consuming. One Present Mode of Operation (PMO) for xe2x80x9cautomaticxe2x80x9d congestion control as opposed to the xe2x80x9cmanualxe2x80x9d approach congestion involves rerouting of an internet call at one tandem switch and destined for an RAS pool connected to one of its egress switches to another RAS pool of the same ISP connected to an egress switch connected to another tandem switch (see FIG. 2). However, such congestion control requires Advanced Intelligent Network (AIN) and Signaling Control Point (SCP) capabilities which may not be supported by some PSTN Class 4/5 switches. Moreover, such congestion control typically only occurs when the originally destined RAS pool has reached saturation level i.e. no more transmission ports are available. Furthermore, such xe2x80x9cautomaticxe2x80x9d congestion control often causes a snowballing effect in the signaling network generated by AIN queries.
In accordance with a first aspect of the present invention, there is provided a switching core controller for controlling at least one Digital Cross-connect System (DCS) each having a switching core, the controller comprising:
(a) at least one router for determining at least one communication path through at least one DCS in response to signaling information; and
(b) at least one resource manager each interfacing with a router of said at least one router for providing instructions for communication path establishment and tear down in the switching core of an DCS of said at least one DCS in response to said signaling information.
By virtue of the first aspect of the present invention, a Digital Cross-connect System (DCS) is effectively converted to a so-called skinny PSTN Class 4 switch having signaling information capabilities. The Switching Core Controller (SCC) of the first aspect of the present invention enables an DCS to be employed for certain service applications including inter alia offloading internet calls from the PSTN, call tapping, and the like, in place of higher switching rate switches. The SCC can be operated in accordance with several modes of operation, for example, a pre-provisioning mode of operation in accordance with a second aspect of the present invention, a load balancing mode of operation in accordance with a third aspect of the present invention, amongst other. The operation of the SCC can be managed in accordance with different management allocation schemes to cater for different loading, for example, the voice call business busy hour at about midday, the voice call residential busy hour at about 5 pm, the internet call residential busy hour between about 9 pm and midnight, weekends as opposed to weekdays, and the like. Management allocation schemes can also reflect different Service Level Agreements (SLAs) between a subscriber and a carrier, desired Grades of Service (GoSs), and the like. The SCC can be implemented for interfacing the DCS with any one of a number of signaling networks including inter alia Q.293 1, MGCP/H.248, Q.SIG, and the like.
In accordance with a second aspect of the present invention, there is provided a method for operating a switching core with at least three interfaces including at least two I/O interfaces with each interface having at least one transmission port, and a switching fabric capable of connecting a pair of transmission ports of two different interfaces of the at least three interfaces for provisioning an end-to-end communication path for passing a particular class of calls of at least two classes of calls through the switching core, the method comprising the steps of:
(a) on the condition that the class of an incoming call matches the class of a pre-provisioned communication path at which it arrives, the pre-provisioned communication path being in accordance with a prevailing management allocation scheme passing the incoming call along the pre-provisioned communication path; otherwise
(b) tearing down the pre-provisioned communication path and replacing it with a new communication path employing the transmission port at which the incoming call arrives, and having a class matching that of the incoming call, and tearing down the new communication path at the termination of the incoming call.
The method in accordance with the second aspect of the present invention is based on the notion that the switching activity of a switching core can be reduced by pre-provisioning communication paths in anticipation of incoming calls which would otherwise effect their establishment, thereby enhancing its switching capability as perceived by a calling party in terms of Grade of Service (GoS), and the like. Moreover, pairs of transmission ports of are preferably continuously being matched as they become available after the tear down of new communication paths such that the number of available communication paths in the absence of any calls passing through the switching core equals the number of pre-provisioned communication paths under a prevailing management allocation scheme.
By virtue of the proposed Future Mode of Operation (FMO) of a switching core in accordance with the second aspect of the present invention, a hitherto employed Tandem Replacement Switch in a post-ingress switch internet call off-loading architecture can be replaced by a less expensive Digital Cross-connect System (DCS), such as the above-mentioned T::DAX(trademark) DCS, without severely impairing the GoS as perceived by a calling party, if at all. Moreover, a switch can be operated in accordance with the proposed FMO in accordance with the second aspect of the present invention, thereby rendering a greater utilization of its inherent high switching rate capability.
In accordance with a third aspect of the present invention, there is provided for a method for routing a call to a transmission port of a mediation device of a pool of at least one mediation device of a logical entity of at least one pool where each of the at least one mediation device of a pool is connected to the same switching core and a logical entity includes at least two mediation devices, the method comprising the steps of:
(a) upon arrival of an incoming call, determining the transmission ports available for handling the incoming call at each of the mediation devices of the logical entity to which the incoming call is directed; and
(b) routing the incoming call to one of the available transmission ports of the logical entity in accordance with a prevailing load balancing allocation scheme.
The method in accordance with the third aspect of the present invention takes advantage of the fact that the occupancy level of the transmission ports of an interface of a switching core having a signaling network interface is known by the signaling gateway, thereby enabling load balancing between mediation devices logically grouped into logical entities for improving their utilization. The term xe2x80x9cload balancing allocation schemexe2x80x9d should be interpreted broadly and not necessarily that the loads are equally balanced between two or more mediation devices. For example, a load balancing allocation scheme can restrict the routing of an incoming call to a sub-set of the available transmission ports of a logical entity. Other allocation schemes can be dependent on the availability of transmission ports of a logical entity, the time of day, SLAs between a subscriber and an ASP, and the like.
The division of mediation devices into logical entities can take into consideration several factors including inter alia the geographical spread of the mediation devices, the geographical spread of the switching cores, the trunks connecting the mediation devices and/or the switching cores, network planning considerations, and the like. As such, one or more network resource management layers are effectively created to manage mediation devices in a fully transparent manner from the point of view of calling parties and/or the carriers including inter alia ILECs, CLECs, ISPs, and the like. A mediation devices can be a RAS pool, a voice switch, an ATM switch, a multi-service switch, and the like.
A particular implementation of the third aspect of the present invention is for load balancing between an ISP""s RAS pools located in business areas and residential areas since an RAS pool is more heavily employed either during office hours or after office hours depending on whether its dial-up connection telephone number belongs to an egress switch located in a business area or a residential area. A natural development of such load balancing is that an ISP can allocate a single internet dial up connection telephone number to all its subscriber""s irrespective of their geographical location.